Reposted. Original article by Muwasala can be found here.
The following is taken from a recent talk by Sayyidi al-Habib Ali al-Jifri (may Allah preserve him and benefit us by him)
According to the Ahl al-Sunnah, the Day of Ashura is a day of joy because of the salvation of Sayyiduna Musa. There is no doubt that it is also a day of sadness since it was the day on which Sayyiduna al-Husayn was martyred along with his relatives and some of the Ansar. At the same time, it is a day of celebration because it was a victory for Sayyiduna al-Husayn. How was it a victory for him when he was killed? It was a victory because he remained true to his principles. It was a victory for truth over weapons and force. When we think of his killers, we think of the fate that is awaiting them. When we remember Sayyiduna al-Husayn, however, our hearts are filled with joy, love and veneration for him and his steadfastness. It is thus a day of victory for Sayyiduna al-Husayn. So if we are joyful for the victory of Sayyiduna al-Husayn and the salvation of Sayyiduna Musa then we are on the right path.
It is natural to feel sadness when we remember the immense injustice that took place. Before dying, Sayyiduna al-Husayn saw all his children killed in front of him, with the exception of Sayyiduna Ali Zayn al-Abidin. He also saw the children of Sayyiduna al-Hasan, the children of his sister Sayyidah Zaynab, and the children of his cousin, Muslim bin Aqil bin Abi Talib, killed in front of him.
There are two extremes, both of which must be rejected. At one extreme we have people who say that it is a terrible day on which no one is allowed to show any joy, and if anyone does so they hate the Ahl al-Bayt. Some people strike themselves and commit other actions which are forbidden in the Sacred Law.
In addition to this, some people think that love for Ahl al-Bayt means showing bad etiquette to Sayyiduna Abu Bakr and Sayyiduna Umar. This is not the way of the Ahl al-Bayt. Sayyiduna Ali had sons named Abu Bakr, Umar and Uthman. Sayyiduna al-Hasan had sons named Abu Bakr and Umar. Sayyiduna al-Husayn had a son named Abu Bakr and two sons named Umar.
There is another extreme. Some people among the Ahl al-Sunnah go the extent to say that Sayyiduna al-Husayn was in the wrong. They praise Yazid, whom the majority of the scholars of Ahl al-Sunnah regard as a corrupt person.
We believe that people that go to either of these extremes are misguided, but at the same time we do not regard them as disbelievers.
It is fine to be sad on this day, and it is fine to be joyful. We must not allow our hearts to be filled with hatred for the perpetrators of this crime, for Allah will take them to account. Instead, our hearts should be filled with veneration for those who were martyred.